This answer is missing LGPE information. If you're not okay with this, then just tell me, and I'll convert my answer to a comment.
RBY: rival (as champion)
FRLG: rival (after Sevii Islands)
Pt: Cynthia (after Stark Mountain)
BW: tie, Alder and Cynthia
BW2: tie, Benga, Janna, Jariel
XY: Diantha (Black Writ)